Provide a home for transient files

plugin/sensible.vim

@@ -47,6 +47,17 @@ set fileformats=unix,dos,mac
 
 set viminfo+=!
 
+if isdirectory(expand('~/.cache/vim'))
+  if &directory =~# '^\.,'
+    set directory^=~/.cache/vim/swap//
+  endif
+  if &backupdir =~# '^\.,'
+    set backupdir^=~/.cache/vim/backup//
+  endif
+  if exists('+undodir') && &undodir =~# '^\.,'
+    set undodir^=~/.cache/vim/undo//
+  endif
+endif
 if exists('+undofile')
   set undofile
 endif